Voice message: variable play back speed (#5121)

* Implement voice message variable playback speed

* Move playback speed string to Untranslated

https://github.com/element-hq/element-x-ios/pull/5121#discussion_r2822631371

* Address review feedback for voice message playback speed

- Persist voice message playback speed as an enum in AppSettings instead of storing an index.
- Update playback speed cycling to derive from enum allCases and safely fall back to `.default` if the stored value cannot be resolved.
- Apply runtime speed updates in AudioPlayer only when the player is in the `.playing` state.
- Keep MediaPlayerProviderTests formatting/indentation style intact while retaining mock playback speed setup.
- Regenerate preview snapshots for:
  - PlaybackSpeedButton
  - VoiceMessageRoomPlaybackView
  - VoiceMessageRoomTimelineView

* Move VoiceMessagePlaybackSpeed outside AppSettings, remove speedRatio

* Stabilize PlaybackSpeedButton width

* Sync voice-message speed label

- Add voiceMessagePlaybackSpeed to TimelineViewState and bind it from appSettings.$voiceMessagePlaybackSpeed.
- Pass that timeline-level speed into VoiceMessageRoomPlaybackView and use it for PlaybackSpeedButton, so labels update consistently across items.
- Use @EnvironmentObject in VoiceMessageRoomTimelineContent so the view re-renders when timeline context state changes.
- In WaveformInteractionModifier, add .allowsHitTesting(showCursor) to the cursor interaction view so hidden pre-playback cursor hit area does not steal taps from the speed button.

ElementX/Sources/Screens/Timeline/TimelineModels.swift

@@ -42,6 +42,7 @@ enum TimelineViewPollAction {
 enum TimelineAudioPlayerAction {
     case playPause(itemID: TimelineItemIdentifier)
     case seek(itemID: TimelineItemIdentifier, progress: Double)
+    case changePlaybackSpeed(itemID: TimelineItemIdentifier)
 }
 
 enum TimelineViewAction {
@@ -114,6 +115,7 @@ struct TimelineViewState: BindableState {
     var isViewSourceEnabled: Bool
     var areThreadsEnabled: Bool
     var linkPreviewsEnabled: Bool
+    var voiceMessagePlaybackSpeed = VoiceMessagePlaybackSpeed.default.rawValue
     
     let hasPredecessor: Bool